On October 26th, explosives opened the Condit Dam in Washington State to allow the free flow of the White Salmon River after 98 years. The reservoir took about two hours to drain, shown here in time-lapse. Read about the dam dismantling project at National Geographic. Link -via the Presurfer

Bill, the Wikipedia page about the dam, and the restoration project, says that there was debate about gradual vs. quick draining, and the conclusion was that quick draining would have less overall impact.